Use multiple processes to find proof

src/mkproof.c

@@ -1,13 +1,20 @@
 #include <assert.h>
+#include <errno.h>
+#include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/types.h>
+#include <sys/wait.h>
 #include <unistd.h>
 #include "argon2.h"
 #include "random.h"
 #include "util.h"
 #include "proof.h"
 
+
+#define MAX_PIDS 512
+
 static void
 die(int check, char *why)
 {
@@ -28,13 +35,8 @@ run_mkproof(argon2_context context, int digits)
 	context.pwd = password;
 	context.pwdlen = sizeof(password);
 
-	unsigned long nattempts = 0;
 	int valid = 0;
 	while (!valid) {
-		if (isatty(STDERR_FILENO)) {
-			fprintf(stderr, "\rAttempt %lu", ++nattempts);
-		}
-
 		ssize_t b = get_random_bytes(password, sizeof(password));
 		assert(b == sizeof(password));
 
@@ -45,12 +47,13 @@ run_mkproof(argon2_context context, int digits)
 	}
 
 	if (isatty(STDERR_FILENO)) {
-		fprintf(stderr, ": found.\nHere is your proof:\n");
+		fprintf(stderr, "Here is your proof:\n");
 	}
 
 	char proof[33];
 	enchex(password, sizeof(password), proof, sizeof(proof));
 	printf("%s\n", proof);
+	_exit(0);
 }
 
 int
@@ -95,18 +98,49 @@ main(int argc, char *argv[])
 		fprintf(stderr, "This may take anywhere from several minutes to a few hours on slow computers.\n");
 	}
 
-	argon2_context context = {
-		.salt = salt,
-		.saltlen = sizeof(salt),
-		.t_cost = iters,
-		.m_cost = memory,
-		.lanes = 1,
-		.threads = 1,
-		.flags = ARGON2_DEFAULT_FLAGS,
-		.version = ARGON2_VERSION_NUMBER,
-	};
+#ifdef _SC_NPROCESSORS_ONLN
+	long nprocs = sysconf(_SC_NPROCESSORS_ONLN) - 1;
+#else
+	long nprocs = 2;
+#endif
 
-	run_mkproof(context, digits);
+	pid_t pids[MAX_PIDS];
+	assert(nprocs <= MAX_PIDS);
+
+	for (size_t i = 0; i < (size_t)nprocs; i++) {
+		pid_t pid = fork();
+		die(pid < 0, "fork()");
+
+		if (pid == 0) {
+			argon2_context context = {
+				.salt = salt,
+				.saltlen = sizeof(salt),
+				.t_cost = iters,
+				.m_cost = memory,
+				.lanes = 1,
+				.threads = 1,
+				.flags = ARGON2_DEFAULT_FLAGS,
+				.version = ARGON2_VERSION_NUMBER,
+			};
+			run_mkproof(context, digits);
+			// unreachable
+			assert(0);
+		}
+
+		pids[i] = pid;
+	}
+
+	int wstatus;
+	pid_t pid = wait(&wstatus);
+
+	for (size_t i = 0; i < (size_t)nprocs; i++) {
+		if (pids[i] == pid) {
+			continue;
+		}
+
+		r = kill(pids[i], SIGTERM);
+		die(r == -1, strerror(errno));
+	}
 
 	return 0;
 }